- ID:
- ivo://CDS.VizieR/J/AJ/144/134
- Title:
- LITTLE THINGS survey of nearby dwarf galaxies
- Short Name:
- J/AJ/144/134
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present LITTLE THINGS (Local Irregulars That Trace Luminosity Extremes, The HI Nearby Galaxy Survey), which is aimed at determining what drives star formation in dwarf galaxies. This is a multi-wavelength survey of 37 dwarf irregular and 4 blue compact dwarf galaxies that is centered around HI-line data obtained with the National Radio Astronomy Observatory (NRAO) Very Large Array (VLA). The HI-line data are characterized by high sensitivity ({<=}1.1mJy/beam per channel), high spectral resolution ({<=}2.6km/s), and high angular resolution (~6"). The LITTLE THINGS sample contains dwarf galaxies that are relatively nearby ({<=}10.3Mpc; 6" is {<=}300pc), that were known to contain atomic hydrogen, the fuel for star formation, and that cover a large range in dwarf galactic properties. We describe our VLA data acquisition, calibration, and mapping procedures, as well as HI map characteristics, and show channel maps, moment maps, velocity-flux profiles, and surface gas density profiles. In addition to the HI data we have GALEX UV and ground-based UBV and H{alpha} images for most of the galaxies, and JHK images for some. Spitzer mid-IR images are available for many of the galaxies as well. These data sets are available online.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/154/102
- Title:
- LMC blue supergiants spectroscopic observations
- Short Name:
- J/AJ/154/102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-quality spectra of 90 blue supergiant stars in the Large Magellanic Cloud are analyzed with respect to effective temperature, gravity, metallicity, reddening, extinction, and extinction law. An average metallicity, based on Fe and Mg abundances, relative to the Sun of [Z]=-0.35+/-0.09 dex is obtained. The reddening distribution peaks at E(B-V)=0.08 mag, but significantly larger values are also encountered. A wide distribution of the ratio of extinction to reddening is found ranging from R_V_=2 to 6. The results are used to investigate the blue supergiant relationship between flux-weighted gravity, g_F_=g/T_eff_^4^, and absolute bolometric magnitude M_bol_. The existence of a tight relationship, the Flux-weighted Gravity-Luminosity Relationship (FGLR), is confirmed. However, in contrast to previous work, the observations reveal that the FGLR is divided into two parts with a different slope. For flux-weighted gravities larger than 1.30 dex, the slope is similar to that found in previous work, but the relationship becomes significantly steeper for smaller values of the flux-weighted gravity. A new calibration of the FGLR for extragalactic distance determinations is provided.
- ID:
- ivo://CDS.VizieR/J/A+A/658/A29
- Title:
- LMC classical Cepheids Fe and O content
- Short Name:
- J/A+A/658/A29
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Classical Cepheids are primary distance indicators and a crucial stepping stone to determining the present-day value of the Hubble constant Ho to the precision and accuracy required to constrain apparent deviations from the LCDM Concordance Cosmological Model. We have measured the iron and oxygen abundances of a statistically significant sample of 89 Cepheids in the LMC, one of the anchors of the local Distance Scale, quadrupling the prior sample and including 68 of the 70 Cepheids used to constrain Ho by the SH0ES program. The goal is to constrain the extent to which the Cepheid luminosity is influenced by their chemical composition, which is an important contributor to the uncertainty on the determination of the Hubble Constant itself and a critical factor in the internal consistency of the distance ladder. We have derived stellar parameters and chemical abundances from a self-consistent spectroscopic analysis based on Equivalent Width of absorption lines. The iron distribution of Cepheids in the LMC can be very accurately described by a single Gaussian with a mean [Fe/H]=-0.409+/-0.003dex and sigma=0.076+/-0.003dex. We estimate a systematic uncertainty on the absolute mean values of 0.1dex. The width of the distribution is fully compatible with the measurement error and supports the low dispersion of 0.069 mag seen in the NIR HST LMC period-luminosity relation. The uniformity of the abundance has the important consequence that the LMC Cepheids alone cannot provide any meaningful constraint on the dependence of the Cepheid Period-Luminosity relation on chemical composition at any wavelength. This revises a prior claim based on a small sample of 22 LMC Cepheids that there was little dependence (or uncertainty) between composition and NIR luminosity, a conclusion which would produce an apparent conflict between anchors of the distance ladder with different mean abundance. The chemical homogeneity of the LMC Cepheid population makes it an ideal environment to calibrate the metallicity dependence between the more metal poor SMC and metal rich Milky Way and NGC 4258.
1044. LMC F supergiants
- ID:
- ivo://CDS.VizieR/J/A+A/293/347
- Title:
- LMC F supergiants
- Short Name:
- J/A+A/293/347
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
- ID:
- ivo://CDS.VizieR/J/AJ/116/723
- Title:
- LMC star clusters ages and metallicity
- Short Name:
- J/AJ/116/723
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Washington system CT_1_ color-magnitude diagrams of 13 star clusters and their surrounding fields that lie in the outer parts of the LMC disk (r>4{deg}), as well as a comparison inner cluster. The total area covered is large (2/3deg^2^), allowing us to study the clusters and their fields individually and in the context of the entire Galaxy. Ages are determined by means of the magnitude difference {delta}T_1_ between the giant branch clump and the turnoff, while metallicities are derived from the location of the giant and subgiant branches as compared with fiducial star clusters. This yields a unique data set in which ages and metallicities for both a significant sample of clusters and their fields are determined homogeneously. We find that in most cases the stellar population of each star cluster is quite similar to that of the field where it is embedded, sharing its mean age and metallicity. The old population (t>=10Gyr) is detected in most fields as a small concentration of stars on the horizontal branch blueward and faintward of the prominent clump.
- ID:
- ivo://CDS.VizieR/J/A+A/586/A41
- Title:
- LMC star clusters catalog
- Short Name:
- J/A+A/586/A41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The main goal of this study is to compile a catalogue of the fundamental parameters of a complete sample of 277 star clusters (SCs) of the Large Magellanic Cloud (LMC) observed in the Washington photometric system. A set of 82 clusters was recently studied by our team. All the clusters' parameters such as radii, deprojected distances, reddenings, ages, and metallicities were obtained by applying essentially the same procedures, which are briefly described here. We used empirical cumulative distribution functions to examine age, metallicity and deprojected distance distributions for different cluster subsamples of the catalogue. Our new sample of 82 additional clusters represents about a 40% increase in the total number of LMC SCs observed to date in the Washington photometric system. In particular, we report here the fundamental parameters obtained for the first time for 42 of these clusters. We found that single LMC SCs are typically older than multiple SCs. Both single and multiple SCs exhibit asymmetrical distributions in log (age). We compared cluster ages derived through isochrone fittings obtained using different models of the Padova group. Although ages obtained using recent isochrones are consistent in general terms, we found that there is some disagreement in the obtained values and their uncertainties.
- ID:
- ivo://CDS.VizieR/J/ApJ/689/983
- Title:
- LMXBs in early-type galaxies. I. Chandra
- Short Name:
- J/ApJ/689/983
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a Chandra survey of LMXBs in 24 early-type galaxies. Correcting for detection incompleteness, the X-ray luminosity function (XLF) of each galaxy is consistent with a power law with negative logarithmic differential slope, {beta}~2.0. However, {beta} strongly correlates with incompleteness, indicating the XLF flattens at low-L_X_. Although the XLFs are similar, we find evidence of some variation between galaxies. The high-L_X_ XLF slope does not correlate with age, but may correlate with [{alpha}/Fe]. Considering only LMXBs with L_X_>10^37^ergs/s, matching the LMXBs with globular clusters (GCs) identified in HST observations of 19 of the galaxies, we find the probability a GC hosts an LMXB is proportional to L^{alpha}^_GC_Z^{gamma}^_Fe_ where {alpha}=1.01+/-0.19 and {gamma}=0.33+/-0.11. The spatial distribution of LMXBs resembles that of GCs, and the specific frequency of LMXBs is proportional to the GC specific luminosity, consistent with the hypothesis that all LMXBs form in GCs.
- ID:
- ivo://CDS.VizieR/J/MNRAS/330/547
- Title:
- Local galaxy ages and metallicities
- Short Name:
- J/MNRAS/330/547
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have assembled a catalogue of relative ages, metallicities and abundance ratios for about 150 local galaxies in field, group and cluster environments. The galaxies span morphological types from cD and ellipticals, to late-type spirals. Ages and metallicities were estimated from high-quality published spectral line indices using Worthey & Ottaviani (1997, Cat. <J/ApJS/111/377>) single stellar population evolutionary models. The identification of galaxy age as a fourth parameter in the fundamental plane (Forbes, Ponman & Brown, 1998ApJ...508L..43F) is confirmed by our larger sample of ages. We investigate trends between age and metallicity, and with other physical parameters of the galaxies, such as ellipticity, luminosity and kinematic anisotropy. We demonstrate the existence of a galaxy age-metallicity relation similar to that seen for local galactic disc stars, whereby young galaxies have high metallicity, while old galaxies span a large range in metallicities. We also investigate the influence of environment and morphology on the galaxy age and metallicity, especially the predictions made by semi-analytic hierarchical clustering models (HCM). We confirm that non-cluster ellipticals are indeed younger on average than cluster ellipticals as predicted by the HCM models. However we also find a trend for the more luminous galaxies to have a higher [Mg/Fe] ratio than the lower luminosity galaxies, which is opposite to the expectation from HCM models.
- ID:
- ivo://CDS.VizieR/J/MNRAS/510/4308
- Title:
- Local main-sequence stars with phot. metallicities
- Short Name:
- J/MNRAS/510/4308
- Date:
- 26 Jan 2022 00:36:57
- Publisher:
- CDS
- Description:
- We present a catalogue of 551214 main-sequence stars in the local (d<2kpc) Galactic thick disk and halo, based on a search of stars with large proper motions (>40.0mas/yr) in the Gaia Early Data Release 3. We derive photometric metallicity calibrated from the colour-luminosity-metallicity distribution of 20047 stars with spectroscopic metallicities, collected from various spectroscopic surveys, including SDSS SEGUE/APOGEE, GALAH DR3, and LAMOST DR6. We combine these results to construct an empirical colour- magnitude-metallicity grid, which can be used to estimate photometric metallicities for low-mass metal-poor stars of K and M subtypes from their absolute G magnitude and colour values. We find that low-mass, high-velocity stars in our catalogue share similar kinematics as reported in recent studies of more luminous Galactic halo stars. The pseudo-kinematic analysis of our sample recovers the main local halo structures, including the Gaia-Enceladus Stream and the Helmi stream; aside from these the local halo stars appear to show a remarkably smooth distribution in velocity space. Since the future Gaia data release will provide radial velocity measurements for only a small number of our sample, our catalogue provides targets of high interest for the future spectroscopic observation programs.
- ID:
- ivo://CDS.VizieR/J/ApJS/227/7
- Title:
- Long & short GRBs with host galaxies data
- Short Name:
- J/ApJS/227/7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Gamma-ray bursts (GRBs) are classified into long and short categories based on their durations. Broadband studies suggest that these two categories of objects roughly correspond to two different classes of progenitor systems, i.e., compact star mergers (Type I) versus massive star core collapse (Type II). However, the duration criterion sometimes leads to mis-identification of the progenitor systems. We perform a comprehensive multi-wavelength comparative study between duration-defined long GRBs and short GRBs as well as the so-called "consensus" long GRBs and short GRBs (which are believed to be more closely related to the two types of progenitor systems). The parameters we study include two parts: the prompt emission properties including duration (T_90_), spectral peak energy (E_p_), low energy photon index ({alpha}), isotropic {gamma}-ray energy (E_{gamma},iso_), isotropic peak luminosity (L_p,iso_), and the amplitude parameters (f and f_eff_); and the host galaxy properties including stellar mass (M_*_), star formation rate, metallicity ([X/H]), half light radius (R_50_), angular and physical (R_off_) offset of the afterglow from the center of the host galaxy, the normalized offset (r_off_=R_off_/R_50_), and the brightness fraction F_light_. For most parameters, we find interesting overlapping properties between the two populations in both one-dimensional (1D) and 2D distribution plots. The three best parameters for the purpose of classification are T_90_, f_eff_, and F_light_. However, no single parameter alone is good enough to place a particular burst into the right physical category, suggesting the need for multiple criteria for physical classification.